Many people in a happy relationship have "in-jokes". But new research has proven that laughing together with your partner is a great tonic for keeping those lovey-dovey feelings going.
Psychologists in the US have found that couples who laugh together, rather than one laughing whilst the other does not, report feeling more satisfied and supported by one another in the relationship.
Interestingly, men who experience a lot of shared laughter in particular report feeling higher levels of passion towards their partner.
The study, carried out by researcher and lecturer Laura Kurtz in the Department of Psychology at the University of North Carolina, is the first to look at what laughter does in a relationship - rather than on the individual person as previous studies have done.
Ms Kurtz said the results showed a clear relationship payback for "shared laughter" over "solo laughter".
"What this means is that we can say that there is something unique about shared laughter for a relationship," said Ms Kurtz. "It isn't just enough to laugh in the presence of your partner - it's the moments where you are both laughing together that really seem to count."
The study was carried out on 77 heterosexual couples who gave responses on how happy they felt with their partner. They were then videorecorded answering questions such as "how did you first meet?". Moments of shared laughter were timed by researchers.
Out of 1,399 laughs, 256 were shared laughs. These were compared to predictors of relationship happiness, such as closeness, commitment, satisfaction and passion.
The results showed that those couples who laughed more together during an interaction in the lab reported feeling closer to and more supported by one another than those who did not.
Oddly, when men laughed they were slightly more likely to spark off shared laughter than the woman laughing - perhaps demonstrating that a male partner with a sense of humour can help keep the relationship light-hearted.
Ms Kurtz said because the study was correlational, it could not directly prove that laughter definitely causes a better relationship - rather, it is linked somehow. Nor is pretending to find your partner funny more often a good idea.
"I would [...] caution against faking a laugh to try to improve your relationship. We tend to be pretty good at detecting whether a laugh is genuine or not, so you don't want to come across as insincere,” she said.
"Rather, I would suggest finding ways to put yourself in situations where you might genuinely laugh with your partner - skip the latest action flick in favour of a comedy.
"If you prioritise the things in your life that might make you and your partner laugh, I would say there is a good chance the behavior is likely to follow."
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